Oil wells are formed from boreholes drilled into a porous, subterranean rock formation containing petroleum. These porous, subterranean rock formations are referred to as petroleum reservoirs or oil reservoirs. Often, a petroleum reservoir is located beneath a less permeable rock layer that traps the reservoir under pressure. In reservoirs under newly developed production, pressure naturally present within the reservoir provides force to allow for the migration of petroleum from the petroleum bearing rock into the borehole forming the oil well. As an oil well produces, pressure subsides until a point is reached where production is no longer economically sustainable, and the oil well is typically abandoned.
An abandoned oil well can potentially contain over half of the original amount of oil in the reservoir; however, a lack of pressure in the reservoir makes continued operation of the oil well economically unproductive without further intervention. Several secondary and tertiary recovery methods have been used to recover additional oil. One method is to inject water or a gas (such as CO2 or nitrogen) into the reservoir to create additional pressure. Polymers and surfactants have also been employed to lower the viscosity of petroleum remaining in the reservoir and aid in petroleum flow. However, such methods are typically costly or potentially impractical in cases where materials are expensive and/or large amounts of water are not locally available.